docs: def parse_class(val):
      """Parse a string, imports the module and returns the class.
  
      >>> parse_class('hashlib.md5')
      <built-in function openssl_md5>
  
      """
      module, class_name = val.rsplit('.', 1)
      module = importlib.import_module(module)
      try:
          return getattr(module, class_name)
      except AttributeError:
          raise ValueError('"%s" is not a valid member of %s' % (
              class_name, qualname(module))
          )